fix: use as many time ticks as d3 can fit on the x-axis

[TCL735]

Closes #135 and influxdata/influxdb#16395

Instead of using 'W' for the average character width, we measure the exact width of the label. Then we ask d3 to give us as many time ticks as will fit on the x-axis with the following restrictions to act as padding around the labels:

• round down when finding the maximum number as the first suggestion to d3
• four or more labels: the sum of all the lengths of the labels is shorter than the available space by at least one label's length
• less than four labels: 0.25, 0.50, 0.75 label length as spacing for one, two, and three labels respectively

[ebb-tide]

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